Photoelectric exposure control for cameras



United States Patent [72] Inventor Karl Wagner Ottobrunn, Germany [21] Appl. No. 695,622

[22] Filed Jan. 4, 1968 [45] Patented [73] Assignee Sept. 1 l 970 Agfa-Gevaert Aktiengesellschaft Leverkusen, Germany [32] Priority Jan. 7, 1967 [33 Germany [3 l A 54,554

[54] PHOTOELECTRIC EXPOSURE CONTROL FOR 1/1964 Waroux Primary Examiner- Norton Ansher Assistant Examiner.loseph F. Peters, Jr. Attorney-Michael S. Striker ABSTRACT: An exposure control for photographic cameras wherein the shutter release pivots or shifts the armature of a stationary electromagnet against the opposition of a spring and simultaneously causes a diaphragm vane to move from an end position in order to furnish a diaphragm aperture reflecting the intensity of scene light. To this end, the winding ofthe electromagnet is connected in circuit with a photosensitive element which enables the electromagnet to attract the armature with a force which is a function of scene brightness and to overcome the bias of the spring so as to move the armature to an end position when the vane assumes a corresponding position to select the proper aperture. The armature then engages and arrests the vane against further movement with or in response to movement of the shutter release.

A guide assembly including a cam mounted on the diaphragm vane or on the armature and a follower on the shutter release serves to determine the extent of movement of the vane or armature in response to progressive displacement of the shutter release.

Patented Sept. 1, 1979 IN V EN TOR.

KARL WANER PHOTOELECTRIC EXPOSURE CONTROL FOR CAMERAS BACKGROUND OF THE INVENTION electromagnet whose winding is connected in circuit with a photoelectric resistor and is arranged to perform pivotal movements as a function of scene brightness to thereby adjust the diaphragm. As it turns from a starting position, the electromagnet causes a spring to store energy and, when the bias of the spring reaches a value which suffices to overcome the force of the electromagnet, the spring arrests the diaphragm in a position which should reflect the intensity of scene light, i.e., the force of the electromagnet. Movements of the diaphragm in response to pivoting of the electromagnet are controlled by a cam, and the position of such a cam must be adjusted with a high degree of accuracy which involves the use of skilled labor. Moreover, the exposure control comprises a large number of complicated parts and, since the electromagnet is not stationary, additional costs arise due to the provision of a rather complicated connection with the source of electrical energy. The shutter release must be provided with sliding contacts which also contributes to the cost and renders the exposure control prone to malfunction. The inertia of the pivotably mounted electromagnet is another factor which is likely to affeet the accuracy of the exposure control so that the latter cannot be mass-produced for use in medium-priced or popularly priced cameras.

SUMMARY OF THE INVENTION It is an object of my invention to provide a novel and improved exposure control which can be mass-produced at reasonable cost for use in inexpensive or medium-priced cameras and wherein the winding of the electromagnet need not move in order to select the exposure value or values as a function of scene brightness.

Another object of the invention is to provide an exposure control wherein the inertia of moving parts is negligible and wherein the exposure values can be selected as a function of scene brightness in automatic response to actuation of the shutter release.

A further object of the invention is to provide an exposure control wherein a single movable setting member suffices to determine that one of a range of exposurevalues which is best suited for an exposure at a given scene brightness.

An additional object of the invention is to provide a novel diaphragm which can be used in an exposure control of the above outlined character.

A concomitant object of my invention is to provide an exposure control which occupies little room and whose assembly requires less skilled labor than presently known exposure controls.

The improved exposure control comprises adjustable setting means (preferably constituted by a movable diaphragm vane which cooperates with a fixed vane) movable between plural positions to furnish a range of exposure values and normally assuming an end position corresponding to an extreme exposure value (for example, to the minimum size of the diaphragm aperture), stationary electromagnet means energizable to produce a magnetic force varying as a function of changes in scene brightness and cooperating with armature means movable from a first to a second end position on energization of the electromagnet means, biasing means for urging the armature means to the first end position, actuating means operative to move the setting means from the aforementioned end position and to move the armature means from the first position toward the second position so that the armature means can move to second position when the force of the electromagnet means overcomes the action of biasing means, and arresting means for arresting the setting means in response to movement of the armature means to second position so that the exposure value furnished by the thus arrested setting means is a function of scene brightness.

The armature means may be mounted for pivotal or reciprocatory movement and the actuating means is preferably constituted by a shutter release which releases the shutter after the setting means is arrested. The winding of the electromagnet means is connected in circuit with a photosensitive resistor or cell which is exposed to scene light so that the strength of current flowing through such winding when the circuit is completed is a function of scene brightness.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved exposure control itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary vertical sectional view of a photographic camera including an exposure control which embodies one form of my invention;

FIG. 2 is a similar fragmentary sectional view of a camera which embodies a modified exposure control; and

FIG. 3 illustrates a third exposure control which constitutes a simplification of the exposure control shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a portion of a still camera which comprises a housing or body 1 having a top wall 1a provided with an opening for the knob 2b of an actuating member 2 here shown as a vertically reciprocable slide provided with elongated slots 5, 6 for fixed pins 7 and 8. The actuating member 2 serves to release the shutter and normally assumes the starting position of FIG. 1 in which its collar 2a bears against the underside of the top wall la. The actuating member is held in such starting position by a return spring 3 which operates between the housing 1 and an arm 4 provided on the actuating member. The pins 7 and 8 are mounted on an intermediate wall or partition of the housing 1. v

The setting means for furnishing a range of exposure values comprises a diaphragm blade or vane 12 which is pivotable on a fixed pin 13 and has an arm 11 bearing against a post 9 of the actuating member 2 under the action of a prestressed helical spring 10. The latter is connected to the arm 11 and to a projection of the actuating member 2. Thus, when the knob 2b of the actuating member 2 is depressed, the spring 10 urges the vane 12 to turn in a counterclockwise direction as indicated by arrow a. The vane 12 is provided with a substantially hornshaped opening 14 which can be moved into lesser or greater registry with the opening defined by a stationary diaphragm vane 15a. The effective size of the aperture depends on the angular position of the vane 12 with reference to the vane 15a. The numeral 15 denotes the objective. In FIG. 1, the vane 12 is shown in that end position in which the diaphragm furnishes an aperture of minimum size.

The vane 12 is further provided with a cutout 16 one side of which is bounded by a serrated portion or ratchet member 17 forming part of arresting means for stopping the vane 12 in an angular position which is a function of scene brightness. The ratchet member 17 can be engaged by a tooth member 18 provided on a one-armed lever 19 which constitutes the armature of an electromagnet including a U-shaped core 27 and a winding 28. The winding 28 is connected in series with a battery 30 or an analogous source of electrical energy and with a photosensitive resistor 29 which is exposed to scene light. A helical spring 25 serves as a means for biasing the armature 19 in a counterclockwise direction, i.e., the spring 25 tends to move the tooth member 18 away from the ratchet member 17. The armature 19 is pivotable on a pin 20 and carries a suitably configurated cam member 21 adjustably affixed thereto by screws 22, 23 or like fasteners. The face 24 of the cam member 21 is tracked by a follower member 26 of the actuating member 2. The members 21, 26 together form a guide means which controls angular displacements of the diaphragm vane 12 in response to depression of the knob 2b.

The operation is as follows:

The electric circuit including the resistor 29, battery 30 and winding 28 includes a master switch (not shown) which can be closed by hand or closes automatically as soon as the knob 2b is depressed to move the actuating member 2 slightly from its starting position shown in FIG. 1. The strength of the current flowing through the winding 28 (and hence the magnetic force produced by the electromagnet 27, 28) is a function of scene brightness because the resistor 29 is exposed to scene light. Thus, the electromagnet then attracts the armature 19 with a certain force which is opposed by the spring 25, the latter tending to maintain the armature 19 in a first end position corresponding to that shown in FIG. 1. In other words, the spring biases the face 24 of the cam member 21 against the follower 26 of the actuating member 2 and thereby keeps the tooth member 18 away from the ratchet member 17 when the actuating member 2 dwells in starting position as well as during a certain portion of movement of the actuating member toward its lower end position. As the operator continues to press the knob 2b, the actuating member 2 travels downwardly and its follower member 26 slides along the cam face 24 so as to turn the armature 19 in a clockwise direction while the diaphragm vane 12 turns in a counterclockwise direction (arrow a) under the bias of the spring 10. The armature 19 approaches the relay 27, 28 and is suddenly moved to a second end position when the magnetic force of the electromagnet overcomes the opposition of the spring 25. The magnitude of such force is a function of scene brightness and the final position of the vane 12 is also a function of such scene brightness because the tooth member 18 can engage the ratchet member 17 to arrest the vane 12 when the electromagnet 27, 28 causes the armature 19 to assume its second end position. The vanes 12 and 15a then define an aperture whose size is properly related to the intensity of scene light. The actuating member 2 continues to move downwardly and releases the shutter in a manner well known from the art. A movable portion of the shutter is shown at 100.

When the magnetic force produced by the electromagnet 27, 28 overcomes the opposition of the spring 25, the armature 19 abruptly moves to its second end position and is held in such end position until after the actuating member 2 opens or permits opening of the aforementioned master switch. The spring 25 is then free to return the armature 19 to its first end post position shown in FIG. 1.

The configuration of the face 24 on the cam 21 is selected in such a way that the extent of angular movement of diaphragm vane 12 changes as a function of changes in scene brightness detected by the receiver 29. This insures that the actual size of the aperture furnished by vanes 12 and 15a reflects accurately the brightness of the scene or subject.

FIG. 2 illustrates a portion of a second camera having a housing or body 31 witha top wall 31a provided with an apening for the knob 32b of an actuating member 32 having two vertical slots 33, 34 for stationary pins 35, 36. A return spring 37 is connected between an arm 38 of the actuating member 32 and the housing 31 to normally bias the actuating member to the starting position shown in FIG. 2 in which a collar 39 of the actuating member bears against the underside of the top wall 31a. The setting means of this camera comprises a diaphragm vane or blade 42 which is turnable on a fixed pivot pin 43 and cooperates with a fixed vane or blade 49 located behind an objective 48. The opening 47 of the vane again resembles a horn, i.e., it comprises a series of portions or sections of different area which can be placed into registry with the opening of the vane 49 in response to pivoting of the vane 42 about the axis of the pin 43. A cam member 41 on the vane 42 has a face which is in engagement with a follower member 40 on the actuating member 32. The vane is further provided with a cutout 45 one side of which is bounded by a serrated portion or ratchet member 46 forming part of an arresting means which further includes a tooth member 52 provided on a horizontal arm of an armature 50. The latter is biased upwardly by a spring 152 so that it normally bears against the lower end face 51 of the actuating member 32. The electromagnet of the exposure control in the camera shown in FIG. 2 comprises a tubular winding 53 which accommodates the vertical arm of the armature 50 and is connected in series with a battery 55 and a photosensitive resistor 54. A spring 44 operates between the vane 42 and housing 31 to bias the face of the cam member 41 against the follower member 40.

When the user depresses the knob 32b, the actuating member 32 first closes a master switch (not shown) in the circuit of the winding 50 so that the strength of the current flowing through this winding is a function of scene brightness because the resistor 54 is exposed to scene light. Thus, the electromagnet exerts upon the armature 50 a magnetic force whose magnitude is also a function of scene brightness, and such force is opposed by the bias of the spring 152 which tends to maintain the armature 50 in the upper end position shown in FIG. 2. As the actuating member 32 continues to move downwardly, its lower end face 51 moves the armature 50 against the opposition of the spring 152 and the follower member 40 simultaneously turns the vane 42 (arrow b) against the opposition of spring 44 and at a rate which is a function of the design of the face on the cam member 41. The opening 47 of the vane 42 moves with reference to the opening of the fixed vane 49 so as to change the size of the diaphragm aperture as long as the vane 42 turns about the axis of the pin 43. When the magnetic force produced by current flowing through the winding 50 overcomes the opposition of the spring 152, the armature 50 suddenly moves to its lower end position and its tooth member 52 engages the ratchet member 46 to prevent further pivotal movement of the vane 42. The actuating member 32 thereupon releases the shutter so that the camera completes an exposure while the size of the diaphrahm aperture reflects the intensity of scene light.

The main difference between the embodiments of FIGS. 1 and 2 is that a portion of the armature 50 shown in FIG. 2 extends into the tubular winding 50 of the electromagnet and that the cam member 41 of the guide means for the vane 42 is provided on this vane rather than on the armature as in FIG. 1. Also, the armature 50 is reciprocable whereas the armature 19 is pivotable with reference to the winding of the electromagnet.

In the embodiment of FIG. 3, the housing or body 101 of the camera comprises a top wall 101a having an opening for the knob 59b of a vertically reciprocable actuating member 59 which is biased to starting position by a helical spring 102 which urges its collar 103 against the underside of the top wall 101a. The armature 65 resembles the armature 50 of FIG. 2 and a vertical arm thereof extends into a tubular winding 66 of the electromagnet. This winding 66 is connected in series with a battery 103 and a photosensitive resistor 104. A spring 68 biases the armature 65 to upper end position by causing it to bear against the lower end face 106 of the actuating member 59. The exposure control of FIG. 3 constitutes a simplification of the exposure controls shown in FIGS. 1 and 2 because the guide means 21, 26 or 40, 41 is dispensed with and the movements of the setting means (constituted by a movable diaphragm blade or vane 57) in response to depression of the actuating member 59 are simply controlled by a spring 58 which biases an arm 56 of the vane 57 against a post 60 on the actuating member. The configuration of the horn-shaped opening 63 in the vane 57 is selected in such a way that the size of the aperture defined by the vane 57 with a fixed vane 107 is a function of scene brightness detected by the photosensitive resistor 104. The vane 57 has a cutout 61 one side of which is bounded by a ratchet member 62 forming part of arresting means which further includes a tooth member 67 on the armature 65. The pivot pin for the vane 57 is shown at 60a, and the numeral 64 denotes the objective.

When the user depresses the knob 5%, the actuating member 59 moves from its starting position and closes a master switch in the circuit of the winding 66. The magnetic force produced by the electromagnet is a function of scene brightness because the resistor 104 is exposedto scene light. The spring 58 causes the arm 56 to remain in abutment with the post 60 so that the vane 57 pivots in a counterclockwise direction (arrow c) and places successive portions of its opening 63 into registry with the opening of the fixed vane 107. The pivotal movement of vane 57 is completed when the magnetic force produced by the electromagnet including the winding 66 overcomes the opposition of the spring 68 and suddenly moves the armature 65 to its lower end position. The tooth member 67 then engages the ratchet member 62 and prevents further movements of the vane 57.

My exponsure control is susceptible of many additional modifications without departing from the spirit of the present invention. For example, the actuating member can be associated with a retard mechanism which prevents premature release of the shutter. Also, the exposure control may be provided with a more sophisticated diaphragm and the actuating member can be arranged to pivot, rather than to reciprocate, between its starting and shutter releasing positions.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

lclaim:

1. in a photographic camera, an exposure control comprising adjustable setting means movable between plural positions to furnish a range of exposure values and normally assuming an end position corresponding to an extreme exposure value; electromagnet means energizable to produce a magnetic force varying as a function of changes in scene brightness and comprising armature means movable from a first to a second position by the magnetic force produced on energization of said electromagnet means whereby the action of said magnetic force on said armature means increases on movement of said armature means from said first position; biasing means for urging said armature means to said first position and for yieldably holding said armature means in said first position with a force which exceeds the maximum force of said electromagnet means; actuating means operative to effect movement of said setting means from said end position and to substantially simultaneously move said armature means from said first position so that said armature means can assume said second position when said magnetic force overcomes the action of said biasing means; and arresting means for arresting said setting means in response to movement of said armature means to second position so that the exposure value furnished by the thus arrested setting means is then a function of scene brightness.

2. An exposure control as defined in claim 1, wherein said electromagnet means comprises winding means and further comprising photosensitive means in circuit with said winding means and exposed to scene light to control the strength of the current flowing through said winding means as a function of scene brightness, said electromagnet means being arranged to attract said armature means.

3. An exposure control as defined in claim 1, wherein said setting means comprises diaphragm vane means and said range of exposure values includes a range of aperture sizes.

4. An exposure control as defined in claim 1, further comprising guide means for determining the rate of movement of said armature means from said first position in response to operation of said actuating means.

5. An exposure control as defined in claim 1, further comprising guide means for determining the rate of movement of said setting means from said end position in response to operation of said actuating means.

6. An exposure control as defined in claim 1, wherein said electromagnet means comprises annular winding means and wherein a portion of said armature means extends into said winding means.

7. An exposure control as defined in claim 1, wherein said actuating means comprises shutter release means movable from a starting position correspondingto said one end position of said setting means to a second position in which said release means actuates the shutter.

8. An exposure control as defined in claim 1, wherein said electromagnet means comprises stationary winding means.

9. An exposure control as defined in claim 1, wherein said setting means is turnable about a fixed axis to and from said end position thereof.

10. An exposure control as defined in claim 1, wherein said armature means is reciprocable between said first and second positions thereof.

11. An exposure control as defined in claim 1, wherein said armature means is pivotable between said first and second positions thereof.

12. An exposure control as defined in claim 1, wherein said biasing means comprises a spring.

13. An exposure control as defined in claim 1, wherein said electromagnet means comprises winding means in series with a source of electrical energy and with a photoelectric resistor which is exposed to scene light.

14. An exposure control as defined in claim 1, wherein said setting means comprises movable diaphragm vane means and said range of exposure values includes a range of aperture sizes, and further comprising stationary diaphragm vane means having a first light-admitting opening of predetermined size, said movable diaphragm vane means having a second opening including a series of portions of different size and said movable vane means being arranged to place successive portions of said second opening into registry with said first opening in response to operation of said actuating means.

15. An exposure control as defined in claim 14, wherein said second opening resembles a horn.

16. In a photographic camera, an exposure control comprising adjustable setting means movable between plural positions to furnish a range of exposure values and normally assuming an end position corresponding to an extreme exposure value; electromagnet means energizable to produce a magnetic force varying as a function of changes in scene brightness and comprising armature means movable from a first to a second position on energization of said electromagnet means; biasing means for urging said armature means to said first position; actuating means operative to move said setting means from said end position and to move said armature means from said first position so that said armature means can assume said second position when said magnetic force overcomes the action of said biasing means; arresting means for arresting said setting means in response to movement of said armature means to second position so that the exposure value furnished by the thus arrested setting means is then a function of scene brightness; and guide means for determining the rate of movement of said armature means from said first position in response to operation of said actuating means, said guide means comprising a cam member and a follower member arranged to track said cam member, one of said members being provided on said actuating means and the other of said members being provided on said armature means.

17. In a photographic camera, an exposure control comprising adjustable setting means movable between plural positions to furnish a range of exposure values and normally assuming an end position corresponding to an extreme exposure value; electromagnet means energizable to produce a magnetic force varying as a function of changes in scene brightness and comprising armature means movable from a first to a second position on energization of said electromagnet means; biasing means for urging said armature means to said first position; actuating means operative to move said setting means from said end position and to move said armature means from said first position so that said armature means can assume said second position when said magnetic force overcomes the action of said biasing means; arresting means for arresting said setting means in response to movement of said armature means to second position so that the exposure value furnished by the thus arrested setting means is then a function of scene brightness; and guide means for determining the rate of movement of said setting means from said end position in response to operation of said actuating means, said guide means comprising a cam member and a follower member arranged to track said cam member, one of said members being provided on said actuating means and the other of said members being provided on said setting means.

18. In a photographic camera, an exposure control comprising adjustable setting means movable between plural positions to furnish a range of exposure values and normally assuming an end position corresponding to an extreme exposure value;

electromagnet means energizable to produce a magnetic force varying as a function of changes in scene brightness and comprising armature means movable from a first to a second position on energization of said electromagnet means; biasing means for urging said armature means to said first position; actuating means operative to move said setting means from said end position and to move said armature means from said first position so that said armature means can assume said second position when said magnetic force overcomes the action of said biasing means; and arresting means for arresting said setting means in response to movement of said armature means to second position so that the exposure value furnished by the thus arrested setting means is then a function of scene brightness, said arresting means comprising a ratchet member and a tooth member, one of said members being provided on said setting means and the other member being provided on said armature means, said other member engaging said one member in the second position of said armature means.

19. An exposure control as defined in claim 18, wherein said tooth member is provided on said armature means. 

